1. Field of the Invention
The invention pertains in a general manner to circuit interfacing in a processor-based electronic system. More particularly, the invention pertains to a programmable control interface device for interfacing a slave circuit requiring complex commands.
2. Description of the Related Art
The complexity of circuits leads to a complexity of command. Among the circuits requiring complex commands may be cited the integrated circuit memories, in particular the large capacity memories of E2PROM or FLASH type. If one wishes to have, for a central processor-based system, a universal memory reader, for example to read memories of different type, it is necessary to have a control interface which is compatible with all the memories available on the market. Such an interface can currently be embodied in two different ways.
A first embodiment consists in performing software management of a standard input/output bus. The central processor then controls the state of each input/output linked to the memory which is linked to input/output ports. The use of a central processor to carry out this kind of function in a software manner requires wide use of the resources of the processor. The central processor is thus almost monopolized by this simple management of the inputs/outputs. Moreover, if an interrupt originating from the system managed by the central processor occurs in the middle of a write or read sequence in the said memory, this sequence is interrupted, and, in certain cases, this may require the complete repetition of the sequence.
A second embodiment consists in using a hardware interface Which itself manages the various possible memories. To do this, the hardware interface must be capable of controlling all the types of memory. Accordingly, it must be furnished with means making it possible to control and sequence each type of memory. A drawback is that the upgrading of the products cannot be taken into account by this type of circuit. In general, when a new circuit to be controlled, such as for example a new memory, a new microcontroller or any other circuit with complex commands, arrives on the market, the hardware interface must then be changed.